Add codegen box test templates for identifiers

compiler/tests-spec/testData/codegen/box/templates/identifiers/enumEntry.kt

@@ -0,0 +1,14 @@
+enum class A(val x: Boolean) {
+    <!ELEMENT(1)!>(false),
+    <!ELEMENT(2)!>(true);
+}
+
+fun box(): String? {
+    if (A.<!ELEMENT(1)!>.x) return null
+    if (!A.<!ELEMENT(2)!>.x) return null
+
+    if (A.<!ELEMENT(1)!>.name != "<!ELEMENT_VALIDATION(1)!>") return null
+    if (A.<!ELEMENT(2)!>.name != "<!ELEMENT_VALIDATION(2)!>") return null
+
+    return "OK"
+}